The present invention relates to electric control circuits and more particularly, to control circuits which transmit a process variable over a radio link. The use of current loops enables the most popular, safe and easy method of transmitting a process variable to a distance limited only by the electromotive force (EMF) which drives the loop. A current loop uses a simple two-wire connection, which allows for fast and simple connection to as many devices, in the loop (in series) as desired, limited only by the EMF of the loop.
Traditional process wireless transmitters are externally powered through the AC mains, or from external direct current voltage sources. Consequently, the use of such traditional transmitters is limited by the power source availability in the vicinity of the transmitter.
It is desirable to provide a process wireless transmitter with the capability of transmitting a process variable over a radio link without requiring an additional external power supply.